{ lib, config, pkgs, ... }:

let
  cfg = config.<namespace>.<name>;
in
{
  options.<namespace>.<name> = {
    enable = lib.mkEnableOption "<description>";

    package = lib.mkOption {
      type = lib.types.package;
      default = pkgs.<package>;
      description = "Package to use";
    };

    settings = lib.mkOption {
      type = lib.types.attrs;
      default = {};
      description = "Configuration settings";
    };
  };

  config = lib.mkIf cfg.enable {
    # Implementation here
  };
}

lib.types.bool
lib.types.str
lib.types.int
lib.types.path
lib.types.package
lib.types.listOf lib.types.str
lib.types.attrsOf lib.types.str
lib.types.nullOr lib.types.str
lib.types.enum [ "a" "b" "c" ]
lib.types.submodule { options = { ... }; }

config = lib.mkIf cfg.enable (lib.mkMerge [
  {
    # Common config
  }
  (lib.mkIf pkgs.stdenv.isDarwin {
    # macOS only
  })
  (lib.mkIf pkgs.stdenv.isLinux {
    # Linux only
  })
]);

let
  platformModule = if pkgs.stdenv.isDarwin
    then ./darwin.nix
    else ./linux.nix;
in {
  imports = [ platformModule ];
}

imports = lib.optional cfg.enableFeatureX ./feature-x.nix;

launchd.daemons.<name> = {
  script = ''
    exec ${lib.getExe cfg.package}
  '';
  serviceConfig = {
    RunAtLoad = true;
    KeepAlive = true;
  };
};

launchd.user.agents.<name> = {
  command = "${lib.getExe cfg.package}";
  serviceConfig.KeepAlive = true;
};

xdg.configFile."<app>/config".text = ''
  # config content
'';

programs.<name> = {
  enable = true;
  package = cfg.package;
  settings = cfg.settings;
};